Wire connector



ET AL Feb. 4, 1969 I H]. aowNs WIRE CQNNEG'I'OR Filed Feb. 13, 1967 INVENTOR. /4 HAROLD H. DOWNS MANUEL A. 1554 United States Patent 3,426,319 WIRE CONNECTOR Harold H. Downs and Manuel A. Issa, Lexington, Ky., assignors to Square D Company, Park Ridge, 111., a corporation of Michigan Filed Feb. 13, 1967, Ser. No. 615,784 U.S. Cl. 339-242 Int. Cl. Hlllr 13/12, 9/12, 7/14 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to electrical connectors and more particularly to a neutral wire connector comprising a neutral bar and cooperating screws and pressure-transmitting clips usable for making electrical connections between either or both aluminum and copper wires of a wire range of different sizes.

There are many problems encountered in the clamping of aluminum wire in an electrical connector. Unless the clamping pressure on the wire is maintained at a relatively constant value despite recurrent heating and cooling cycles, the aluminum of the wire flows out of the clamping area at periods of high clamping pressure leaving less aluminum within the clamping area at periods of low clamping pressure resulting in lower than normal clamping pressure during those periods. This often leads to excessive temperature rise because of the formation of oxides on the wire at the clamping area when a'predeterrnined minimum clamping pressure is not maintained. Further, aluminum wire is relatively soft and is therefore easily deformed by the connector often resulting in a material reduction in cross sectional area and in the weakening or even severance of the wire. In addition, the ability of aluminum wire to withstand repeated flexing without breaking is greatly limited by the presence of nicks or notches on the surface often caused by the connector.

A neutral wire connector in accordance with the present invention comprises an extruded aluminum body, a steel clamping screw, and a spring steel pressure-transmitting clip of improved configuration which cooperate to maintain substantially constant clamping pressure on either aluminum or copper wires of a wide range of sizes. The clip and the wire-receiving opening in the metal body are so shaped that the possibility of mechanical damage to aluminum wire which can lead to breakage of the wire is minimized.

When the invention is incorporated in a neutral wire connector intended to accommodate a wide range of wire sizes, the wire-receiving openings in the neutral bar preferably are of two different sizes of wire. Respective grooves or slots formed at the bottom of the openings of either size receive solid wires of the smaller sizes and have dimensions such that the upper portions of the smaller wires extend upwardly from the slots into the major portions of the openings to permit clamping by the spring clips. Solid wires of larger sizes may be received in the major portions of the openings of either size, the slots being so dimensioned that, upon pressure 3,426,319 Patented Feb. 4, 1969 being exerted by the screws and clips, portions of the wires are deformed into the slots without substantial reduction in their cross-sectional areas. Stranded wire of a still larger size may be received and clamped in the larger openings with some of the strands entering the slots and the remainder being guided into position for effective clamping.

Each of the spring clips has a downwardly convex and upwardly concave clamping portion which provides several unexpected advantages that were discovered from experiments with several different shapes. Although the clips of this application having such a concavo-convex clamping portion perform better by actual test in slotted openings and result in a more reliable connection of the various sizes of aluminum and copper wire than other clips, for example such as those disclosed in Millermaster Patent No. 2,193,202 issued Mar. 13, 1940, and Curtis Patent No. 3,260,989 issued July 12, 1966, the reasons for the improved performance are not completely understood. One of the unexpected advantages is that the slots in the lower portions of the wire-receiving openings of the neutral bar can be made deeper and wider than would otherwise be practical for small wires, thereby to render the openings suitable for clamping larger wires as well. Another advantage of the curved shape of the clamping portion :of the clip is that the clamping portion aligns itself with the axis of the clamping screw so as to become centered in the wire-receiving opening. The curved shape also prevents the clamping portion fromdigging into the softer aluminum of the neutral bar.

An object of the present invention is to provide an improved neutral wire connector comprising an improved pressure-transmitting clip in combination with a neutral bar having complementary wire-receiving openings for reliably clamping, in permanent electrical contact, aluminum or copper wires of a plurality of different sizes.

Another object is to provide an improved neutral wire connector comprising a neutral bar having a plurality of wire-receiving openings shaped to cooperate respectively with concavo-convex clamping portions of pressuretransmitting clips.

Another object is to provide an improved pressuretransmitting clip for use with a neutral bar.

A further object is to provide an improved clip for use with a neutral bar and which has an outwardly convex clamping portion.

Other objects and advantages of the invention will become apparent from the following specification wherein reference is made to the drawings in which:

FIG. 1 is a perspective view of a portion of a neutral wire connector in accordance with the present invention;

FIG. 2 is an exploded view of a clamping screw, a pressure-transmitting clip, and a portion of a neutral bar of the neutral wire connector of FIG. 1;

FIG. 3 is a top plan view of the spring clip;

FIG. 4 is a sectional view of the spring clip taken along the line 44 of FIG. 3;

FIG. 5 is a front view of the spring clip; and

FIG. 6 is an elevational view of the connector of FIG. 1 with clamped wires of various sizes shown in cross section.

Referring to FIG. 1, a connector body in the form of a neutral bar 10, which may be of any desired length, has a plurality of longitudinally spaced openings 11 of uniform diameter extending inwardly from a top wall 12 and intersecting respectively a plurality of like-spaced wire-receiving openings 14 and 15 extending transversely through the bar 10 between the side walls thereof parallel to the top wall 12. A neutral bar of this type is shown in Patent No. 3,228,094 of Harris I. Stanback and Alfred Mueller which issued on Jan. 11, 1966, to the assignee of the present invention. The openings 14 are relatively small and the openings are relatively large and are alternately arranged along the length of the bar 10. Wires of various sizes are received in the openings 14 and 15, as will be described, and the openings 11 receive respective clamping screws 19 and may be pre-threaded or the screws 19 may be of the thread-cutting type.

The wire-receiving openings 14 and 15 have generally rectangular grooves or slots 14a and 15a, respectively, in their bottom portions parallel to the axes of the openings 14 and 15 and extending the full length of the openings 14 and 15. As shown in the drawing, the upper and lower wall portions of the smaller openings 14 are generally cylindrical and are joined smoothly by planar opposing side wall portions so as to provide non-angular internal surfaces exclusive of the slots 14a. The upper wall surfaces 15b of the larger openings 15 are cylindrical, but each opening 15b has pairs of contiguous flat slanted surfaces 15c and 15d leading to the respective upper edges of its associated slot 15a. If desired, the smaller openings 14 could have similar slanted surfaces. The slots 14a and 1511 may be of the same size and shape or the slots 14a may be slightly deeper and narrower than the slots 15a.

Each of the clamping screws 19has a head portion 19a, defining a downwardly facing annular surface 191), and an unthreaded neck portion 190 of material length and of lesser diameter than the threaded portion. A plurality of identical clips 20 of improved configuration are connected to the clamping screws 19, respectively, as will be described.

The neutral bar 10 is preferably aluminum, the screws 19 are preferably steel, and the clips 20 are preferably spring steel. This combination of metals is important for the coordination of heat expansion characteristics so that the connector is eminently suitable for retaining either aluminum or copper wires.

Each of the spring clips 20 is generally U-shaped with an upper leg portion 21 connected to a concavo-convex lower leg portion 22 by a bight portion 24. The upper leg portion 21 is split centrally by an elongated slot 25 defining a pair of prongs 26 and 27. The slot 25 intermediate of its ends has a pair of concentric circular arc portions 28 sized to snugly receive the neck portion 190 of one of the clamping screws 19. At the outer free end of the leg portion 21, the slot 25 is flared outwardly so as to cause the prongs 26 and 27 to be resiliently spread apart as they initially engage the reduced diameter neck portion 190 of one of the clamping screws 19. Each of the prongs 26 and 27 has a transversely-directed, downwardly-convex bowed or embossed portion 29 aligned with the arc portions 28 and of a depth related to the axial length of the reduced diameter portion 190 thereby to prevent undesirable lost motion between the clip 20 and the screw 19 axially of the screw and of a depth greater than the pitch of the threads of the screw thereby to prevent the upper leg portion 21 from engaging the threads when the screw is backed out.

The lower leg portion 22 of each of the clips 20 and a lower portion of the bight portion are narrower than the remainder of the bight portion 24 defining downwardlydirected shoulders 22a and 22b. As mentioned, the lower leg portion 22 is concavo-convex, the longitudinal arcuate bend defining a downwardly facing convex clamping surface 30 and an upwardly facing concave surface 31, the axis of the bend being parallel to the axes of the wirereceiving openings 14 and 15 when the clip 20 is in place in one of the openings as shown in FIGS. 1 and 6.

To assemble the neutral connector, the clamping screws 19 are threaded a short distance into the respective openings 11 of the neutral bar 10 and then the clips 20 are pressed into connective engagement with the respective screws 19. In each instance this involves forcing the pair of prongs 26 and 27 of the upper leg portion 21 of each of the clamps 20 resiliently outwardly as they ride laterally oppositely on the reduced neck portion 190 of the associated clamping screw 19 until the neck portion 19c seats snugly within the arcuate portions 28 of the slot 25. Concurrently with the engagement of the upper leg portion 21 on the clamping screw 19, the lower leg portion 22 is received in the associated one of the openings 14 and 15 so that the upwardly concave portion 31 fits under a preferably rounded or chamfered bottom portion 19d of the clamping screw 19 in self-centering contact therewith. The lower leg portion 22 is long enough to extend into a respective one of the openings 14 or 15 beyond the clamping screw 19 for a relatively small dis tance permitting the free end of the portion 22 to dig into an aluminum wire thereby to insure good gripping action. The nicking or scoring of the wires beyond the clamping screw 19 does not affect the ability of the wire to withstand flexing because all of the flexing takes place on the side of the clamping screw facing the bight portion 24.

Operation of the neutral connector in clamping wires is different for the various gauges of wire, but is generally similar for both copper and aluminum. This is indicated for the described embodiment in FIG. 6. The smaller wire sizes, for example, No. 12 and 14 gauge, may be inserted directly into either of the slots 14a or 15a. In FIG. 6, No. 14 and No. 12 gauge wires are shown received in the slots 14a at A and B respectively. Both of the slots 14a and 15a are shallow enough so that portions of wires of these sizes extend upwardly beyond the slots a sufficient distance to permit clamping by the lower leg portions 22 of the clips 20 with pressure exerted against the bottom of the slots. Somewhat larger sizes of wire, for example, No. 10 and No. 8 gauge, are inserted into the larger part of the Openings 14 and 15, and the width of the slots 14a and 15a is such that the wires are deformed by the clips 20 into the slots without a material loss of overall cross-section. This is indicated at C in FIG. 6 for No. 8 gauge wire and at D for No. 10 gauge wire. Still larger wires, such as stranded wire of N0. 6 gauge, may also be inserted into either of the openings 14 or 15. A No. 6 gauge stranded wire is shown clamped in one of the openings 14 at E in FIG. 6. As the curved lower leg 22 of one of the clips is brought to bear against a stranded wire of this size by tightening of the associated one of the clamp- .ing screws 19, a portion of the wire also deforms into the slots 14a or 15a, thus increasing the gripping strength of the connection. Only the larger openings 15 can accommodate No. 4 gauge stranded wire, and a portion of the wire of this size is deformed into the slot 15a by the clamping action as shown at F in FIG. 6.

From the foregoing, it will be seen that the smaller openings 14 accommodate No. 6 through No. 14 wire and the larger openings 15 accommodate No. 4 through No. 14 wire. Since the openings 14 and 15 are alternated along the length of the bar 10, there is an equal chance of No. 6 through No. 14 wires being installed in either of the openings 14 and 15. No. 4 wire, of course, must always be installed in one of the larger openings 15. Wire of this size usually has seven strands, and for this reason, the larger openings are preferably provided with the fiat surfaces 15c and 15d. The strands are forced along the surfaces 15c and 15d as indicated at F in FIG. 6, some of the strands entering the slot 15a and the surfaces and 15d guiding the remaining strands and the lower leg portion 22 of the clip 20 toward the center of the opening 15 as it approaches the bottom. The angular shape of the walls 150 and 15d prevents the leg 22 from sticking at one spot by its side edges digging into the walls.

In the case of the smaller openings 14, it is not necessary that the wire or the lower leg 22 be guided toward the center of the opening and, thus, slanting surfaces are unnecessary. They could be used, however, but the circular shape is easier to manufacture.

As mentioned hereinbefore, the depths of the slots 14a and 15a are such that a small amount of deformation occurs upon the clamping of aluminum wire of sizes No. 8 through No. 12. The pressure exerted by the lower leg portion 22 changes the cylindrical cross section of the wire to a generally ovate shape Without materially reducing the cross-sectional area. The Wire is deformed trans versely but not stretched. The optimum depth of the slots 14a and 15a for these three sizes of wire is slightly greater than would be most desirable for No. 14 wire. However, because of the curvature of the lower leg portion 22, size 14 wire is also tightly held.

One of the advantages of the concavo-convex shape of the leg portion 22 is to clamp the No. 8 through No. 12 wires against the sides of the slots 14a and 15a as well as against the bottom of the slots. The curved shape tends to form the wire into an ovate cross-section with practically no elongation of the wire. A further benefit of the curved shape of the leg portion 22 is that it tends to center under the rounded end face of the screw 19.

We claim:

1. A neutral wire connector assembly comprising an elongated generally rectangular electrically conductive solid bar having relatively long and short cross sectional dimensions and having a first plurality of holes extending therethrough in the direction of the short cross sectional dimension and in spaced relationship longitudinally of the bar and a second plurality of holes extending partially therethrough in the direction of the long cross sectional dimension into axially intersecting relationship respectively with said first plurality of holes, each of said first plurality of holes having a slot portion of rectangular cross section disposed opposite the respective one of said second plurality of holes and forming a continuous channel extending through the bar and having greater width than depth, a plurality of clamping screws threaded respectively into said second plurality of holes, and a plurality of generally U-shaped clips each having a first leg portion disposed outside said bar and secured to a respective one of said clamping screws adjacent a head portion thereof and a second leg portion disposed inside said bar in a respective one of said first plurality of holes between an inner clamping end portion of the respective clamping screw and the slot portion of the hole, the second leg portion extending parallel to the slot portion, having a curved cross section, and presenting a concave surface to the clamping screw and a convex surface to the slot portion of the hole.

References Cited UNITED STATES PATENTS 2,499,985 3/1950 Cafiero 339272 2,943,294 6/ 1960 Norden 339242 2,976,514 3/1961 Standback et a1 339-272 3,228,094 1/1966 Stanback et al. 339272 X 3,260,989 7/1966 Curtis 339-272 FOREIGN PATENTS 1,241,326 8/1960 France.

901,304 1/1954 Germany.

177,277 11/1961 Sweden.

OTHER REFERENCES Germany printed application 1,104,013, April 1961.

MARVIN A. CHAMPION, Primary Examiner.

P. TEITELBAUM, Assistant Examiner.

US. Cl. X.R. 

